Heat assisted magnetic recording (HAMR) generally refers to the concept of locally heating a recording media to reduce the coercivity of the media so that an applied magnetic writing field can more easily direct the magnetization of the media during the temporary magnetic softening of the media caused by the heat source. A tightly confined, high power laser light spot can be used to heat a portion of the recording media. Then the heated portion is subjected to a magnetic field that sets the direction of magnetization of the heated portion. With HAMR, the coercivity of the media at ambient temperature can be much higher than the coercivity during recording, thereby enabling stability of the recorded bits at much higher storage densities and with much smaller bit cells.
One approach for directing light onto recording media uses a laser diode mounted on a read/write head (also referred to as a “slider”). The laser diode directs light to a planar waveguide that transmits the light to a small spot adjacent to an air bearing surface of the slider. A near-field transducer (NFT) can be included to further concentrate the light. The near-field transducer is designed to reach a local surface plasmon (LSP) condition at a designated light wavelength. At LSP, a high field surrounding the near-field transducer appears, due to collective oscillation of electrons in the metal. Part of the field will tunnel into an adjacent media and get absorbed, raising the temperature of the media locally for recording.
A significant consideration for heat assisted magnetic recording (HAMR) is the location of a laser diode that is used as the optical power source. One current design places a laser diode on the top of a slider. Radiation from the laser diode is focused and directed to coupling grating on the waveguide using external optical elements. This method requires the development of the external optical elements and could be implemented by assembling the sliders one-by-one and using active alignment.
A potential embodiment integrates a laser diode into the trailing edge of the slider and uses a waveguide coupler to guide the laser to the near field transducer using a combination of light-positioning elements such as solid immersion mirrors (SIMs) an/or channel waveguides. Proper alignment between the laser diode and the waveguide is needed to achieve the desired coupling of light from the laser to the waveguide. In addition, this needs to be accomplished in a cost-effective manner.